Nice To Know: You might also hear the term cardiac output used to describe the amount of blood thats pumped through the body. Cardiac output is simply the amount of blood pumped out of a ventricle in one minute: Cardiac output = Heart rate x Stroke volume (amount of blood pumped with each beat) As cardiac output increases, so does blood pressure. This is why heart rate and stroke volume are important ways for the body to control blood pressure. How difficult it is for blood to travel around the body (peripheral resistance). The third major component that affects the blood pressure is the caliber or width of the arteries. Blood traveling in narrower vessels encounters more resistance than blood traveling through a wider vessel (its harder for water to pass through a narrow pipe than a wide pipe). Depending on what a person is doing, the amount of blood the heart pumps varies enormously. Yet the blood pressure normally remains pretty stable. Thats mainly because the body adjusts the resistance of the arteries, either widening or narrowing the m as appropriate, to prevent the blood pressure from swinging wildly. This ability to regulate the width of the blood vessels is called the peripheral resistance. Most of the resistance to blood flow in the circulation occurs in the small-diameter arteries called arterioles. These arterioles are especially important in the immediate regulation of blood pressure. Thats because they contain specialized smooth muscle in their walls that can relax or contract, allowing the blood vessel to get wider or narrower.
Posted on: Sun, 06 Apr 2014 16:15:00 +0000
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